GB2159801A - Containers and closures therefor - Google Patents

Abstract

In order to prevent backing-off of a plastics screw closure for a glass container having a multi-start thread (14), axially directed protruding ribs (30) are formed on the container neck below the container threads in axial alignment with spaces (15) between the thread, and axially directed channels (17) are formed on the interior of the closure skirt adjacent the free edge thereof for receiving the ribs. Two ribs are provided, diametrically disposed on the container neck; the channels are arranged as four pairs which are disposed substantially at 90 DEG intervals around the closure. Diametrically associated channel pairs are offset in opposite rotational senses by one quarter of a cavity pitch from their associated diameter; this ensures that at least one of the ribs can always engage within a channel dispite small variations of the relative angular position of the closure and container due to manufacturing tolerances etc. <IMAGE>

Description

SPECIFICATION Containers and closures therefor This invention relates to packaging containers and closures therefor.

It is well known to close a packaging container of a food or other product with a screw closure, the container and closure having complementary screw-thread formations which are engageable together to secure the closure over the container mouth in a position to form a seal with a suitable finish provided on the container. Each screw-thread formation may be a single thread usually having a single turn, or it may be a multi-start thread in which case each thread portion will usually extend for only a portion of a turn. One example of a thread formation of the latter kind for a closure is a four-start thread of which the four thread portions are regularly spaced around the closure and each extends for approximately 65 of subtended angle at the closure central axis.

A particular difficulty encountered with screw closures in use is "backing-off", that is, the tenancy of the closure after application to loosen itself by movement in the direction of unscrewing, and so possibly to impair the integritiy of the seal which it provides. Backing-off is a particularly prevalent problem for multi-start threads because of the relatively large helix angle of each thread portion, and in situations where the closed container is subject to substantial vibration or repeated thermal cycling; however, even for closures with a single start thread having a relatively small helix angle, backing-off can be a problem if, for example, a long shelf life is required for a highly oxygen sensitive product.

Various expedients have been proposed in the past for preventing backing-off of screw closures, amongst which are modifications of the thread formation of the screw closure and/or of the container to generate additional frictional resistance to unscrewing. Such expedients have usually, however, had the adverse effect that the closure requires a high torque for unscrewing if it is to be sufficiently tightly screwed on to ensure proper sealing.

Thus, whilst backing-off has been prevented or rendered harmless, the closure has suffered instead from difficulties with removal by the consumer, particularly those consumers of a weak or arthritic disposition.

It is a primary object of the present invention to provide an arrangement of screw closure and container, which may combine a substantial degree of resistance to backing-off with ease of unscrewing as and when this is required. Accordingly, the invention provides a container and closure combination, the container having a mouth-defining, generally cylindrical portion externally formed with a screw thread formation, the closure having a closure panel to close the container mouth, and a depending, generally cylindrical skirt internally formed with a screw-thread formation for engagement with the screw-thread formation of the container to secure the closure on the container, beyond the respective screw-thread formation (in relation to the container mouth or the closure panel as appropriate), one of the said container portion and the closure skirt being formed with at least one protruberance and the other being formed with at least one cavity, a said protruberance being resiliently located within a said cavity when the closure is fully engaged on the container to provide a releasable catch resisting backing-off of the closure.

Preferably the closure is moulded from a thermoplastics material and is formed with the cavity as an elongate channel directed axially of the closure skirt and opening into the skirt free edge. The protruberance is then provided on the container, which may be of glass or of plastics.

As will become apparent from the embodiment now to be described, more than one protruberance may be provided, and more than one cavity can be provided for the or each protruberance to allow for differences in the angular relationship of the closure and container when the closure is fully engaged.

The embodiment is now described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a plastics screw closure in accordance with the invention, as seen in section on the diametral plane ll-ll of Fig.2: Fig.2 is a full plan view of the closure as seen looking on the free edge of the closure skirt; Fig.3 shows the bottle neck on which the screw closure is to be fitted, as seen in section on the nearly diametral plane Ill-Ill of Fig.4; Fig.4 shows the bottle neck partly in pian view and partly in section, being a view on the line IV-IV of Fig.3; Fig.5 is an enlarged scrap view of the closure/container combination, as seen on the section line V-V of Fig.3 when the closure is fitted; and Fig.6 correspondingly shows the closure/container combination on the section line VI-VI of Fig.2.

Referring firstly to Figs. 1 and 2, a unitary screw closure for a bottle is moulded from a suitable thermoplastics material such as high density polyethylene, and in conventional manner comprises a generally plane closure panel 10 and a depending, generally cylindrical skirt 11 extending to a free edge 1 2.

An annular and compliant sealing fin 1 3 is located within the closure at the junction of the skirt with the closure panel and arranged in known manner to form an hermetic seal with the finish on the bottle neck to which the closure is fitted.

For attaching it to the bottle neck the closure has a conventional four-start thread the four identical thread portions 14 of which are regularly spaced around the skirt and each subtends approximately 65 of angle at the central axis XX of the closure. Adjacent ones of the thread portions are separated by gaps 15.

The skirt 11 has an internal surface 1 6 which extends from the base of the sealing fin 1 3 to the free edge 1 2. This surface is cylindrical, except for its interruption by the thread portions 14 and with the further exception of four pairs of adjacent. elongate and identical cavities 1 7 which are formed in the skirt adjacent and open to its free edge 12.

As can be seen from Figs.5 and 6 in particular, each cavity extends axially of the skirt 11 from its open bottom end in the free edge 1 2 to, at its top end, a flat transverse surface 1 8 parallel to the free edge 12. The back (i.e. radially outer) wall 1 9 of each cavity is arcuate e.g. part-cylindrical, and directed axially of the closure, the cavities of each pair being immediately adjacent one another so as to share a common line of intersection of their back wall 1 9 with the internal surface 1 6 of the skirt 11.

The angular positions of the four cavity pairs in relation to the closure are fully described below; suffice it to say for the moment, however, that generally they correspond with the gaps 1 5 between the thread portions 14.

The bottle neck 20 on which the closure is to be fitted is shown in Figs. 3 and 4 to which reference is now made. The neck forms part of a glass bottle only the neck and an upper part of the shoulder 21 of which are shown for clarity.

The neck has a free edge 22 surrounding the bottle mouth 24 and forming a-top annular sealing surface for engagement by the closure fin 13.

For engagement with the four thread portions 14 on the closure the bottle has a corresponding number of complementary thread portions 25 moulded to project from the generally cylindrical external surface 26 of the bottle neck. The surface 26 extends between the free edge 22 and its top end and a continuous peripheral bead 27 at its bottom end. Like the thread portions 14 of the closure, the thread portions 25 of the bottle are identical to one another; each portion occupies approximately 100" of subtended angle at the central axis YY of the bottle so that the portions overlap at their ends. The overlapping regions of portions are denoted 28 in Fig.4.

As thus far described the bottle is conventional. In accordance with the invention, however, it is modified by the provision of two protruberances in the form of short ribs 30 which project outwardly from the surface 26 of the neck immediately above the bead 27.

Each rib 30 in cross-section presents a generally rounded crest 31 having a radius of curvature which is approximately the same as, and preferably somewhat smaller than, that of the back wall 19 of each cavity 1 7. It extends along the surface 26 parallel to the central axis YY of the container, from the bead 27 at its bottom end to a smoothly rounded free end 33 forming top end of the rib (Fig.6). It is of substantially the same depth (radially of the container) as the bead 27, its crest 31 merging smoothly into the crest (unnumbered) of that bead; it therefore projects radially beyond the thread formations 25.

The ribs 30 are disposed diametrically opposite one another in relation to the bottle neck, at a suitable position for entering the cavities 1 7 as is described later.

Figs. 5 and 6 show a detail of the closure when in its fully engaged position on the bottle neck. In known manner the thread portions 14, 25 of the closure and bottle then engage to hold the closure in position, the sealing fin 1 3 engaging the free edge 22 of the bottle neck to form a desired hermetic seal for a product in the bottle. The product may, for example, be a sauce product.

Backing-off of the closure such as might occur if the bottle were subject to substantial vibration and/or thermal variation over an extended period of time, is prevented by latching engagement of the ribs 30 and cavities 1 7 as is now described.

Rather than being disposed diametrically opposite one another as are the ribs 30, opposite pairs of the cavities 1 7 are offset in relation to one another by one-half of the width of one cavity, that is to say, by one-half of a cavity pitch. Thus, in each of the two pairs of opposed cavities one pair is advanced (circumferentially of the closure) by one-quarter of a cavity pitch in relation to the median line of the respective gap 1 5 between thread portions 14, whereas the other pair is retarded from the respective median line by the same distance.

The half-cavity pitch by which the pairs of opposed cavities are offset from one another together with the provision of two cavities instead of only one per group, ensures that despite manufacturing tolerances of the bottle and the closure, and despite such extraneous effects as elevated temperatures and plastics creep, at least one of the ribs 30 will move into a cavity 1 7 as the closure is being applied. During the movement, some distortion of the closure skirt 11 in the vicinity of the engaged rib will occur, as is shown exaggerated in Fig.5. When the closure is fully home the residual stresses in the skirt will hold it frictionally and in a resilient manner in contact with the rib.Moreover, any tendancy of the closure to backing-off will be resisted not only by this frictional resistance but also by the additional resistance generated by the additional distension of the skirt caused by any movement of the rib out of the cavity.

The total resistance presented by the engaged rib to backing-off of the closure is therefore substantial, and sufficient to prevent backingoff from occurring under normal conditions of use. It is, however, insufficient to prevent a consumer, even one of a frail disposition, from unscrewing the closure in the normal manner as and when required.

It is to be noted that because of the substantial helix angle of the thread formations 14, 25, the rib 30 will enter and leave the cavity 1 9 With a substantial vertical component of direction in addition to the component perpendicular to the axis of the container/ closure combination. The rounded top end 33 of the rib is provided to assist the rib to move into and out of the cavity by camming engagement with the top face 18 of the latter.

In a similar way the rounded crest 31 of the rib will assist the movement of the rib past the side edges of the cavity.

The invention is not limited in application to container/closure combinations with multistart, part-turn thread formations as particularly described, and may have application where single-start threads are employed. In a non-illustrated embodiment of the invention a plastics screw closure for a glass or plastics bottle has a single start thread with one turn for co-operation with a like formation on the bottle. Cavities similar to the cavities 1 9 of the described embodiment are provided regularly around the whole periphery of the closure skirt adjacent its free edge, and one or more ribs are provided on the bottle to provide back-off resistance in accordance with the invention; advantageously, two diametrically disposed ribs are provided and an odd number of cavities is used so that diametrically opposed cavities are offset by one half of a cavity pitch.

The one or more cavities and protruberances of a closure/container combination in accordance with the invention may have other forms than those particularly shown and described; for example, the cavities may be in the form of dimples, and the protruberances in the form of rounded pimples. Furthermore, the cavities may be provided on the container, and the protruberances on the closure.

Whereas in the described embodiment each protruberance is selectively engageable in one of two or more mutually adjacent cavities, if desired a cavity may be selectively engaged by any one of two or more mutually adjacent protruberances.

In the described embodiment the location of the cavities adjacent to, and opening into, the skirt free edge 1 2 is in order to facilitate ejection of the closure from the mould in which it is formed. Likewise, and again because of moulding considerations, the ribs 30 are preferably located at a 90 angular spacing from the mould line of the bottle.

Claims (10)

1. A container and closure combination, the container having a mouth-defining, generally cylindrical portion externally formed with a screw-thread formation, the closure having a closure panel to close the container mouth, and a depending, generally cylindrical skirt internally formed with a screw-thread formation for engagement with the screw-thread formation of the container to secure the closure on the container, beyond the respective screw-thread formation (in relation to the container mouth or the closure panel as appropriate), one of the said container portion and the closure skirt being formed with at least one protruberance and the other being formed with at least one cavity, a said protruberance being resiliently located within a said cavity when the closure is fully engaged on the container to provide a releasable catch resisting backing-off of the closure.

2. A combination as claimed in claim 1, which includes, for the or each protruberance or cavity, two or more mutually adjacent cavities or protruberances (as appropriate) located for individually and selectively engaging the protruberance or cavity in dependence upon the angular relationship of the closure and the container when the closure is fully engaged.

3. A combination as claimed in claim 2, which includes two protruberances or cavites diametrically disposed in relation to the respective container ortlosure, for engaging the protruberances or cavities the closure or container (as appropriate) having respective frst and second groups of mutually adjacent cavities or protruberances, the groups being centred on a diametral line of the closure or container but offset in opposite rotational directions in relation thereto.

4. A combination as claimed in claim 3, wherein the groups of cavities or protruberances are offset by one quarter pitch of a said cavity or protruberance from the said diametral line.

5. A combination as claimed in any preceding claim, wherein the closure is moulded from a thermoplastics material and is formed with the or each said cavity as an elongate channel directed acially of the closure skirt and opening into the skirt free edge.

6. A combination as claimed in claim 5, wherein the container is formed with the or each protruberance as an elongate rib formed on, and directed axially of, the container portion, the end of the rib nearest the container mouth being rounded.

7. A combination as claimed in claim 6, wherein the container is of glass.

8. A combination of container and closure, substantially as herein described with refer ence to the accompanying drawings.

9. The container of or for a combination as claimed in any preceding claim.

10. The closure of or for a combination as claimed in any preceding claim.