GB2025380A

GB2025380A - Seals between containers and closures therefor

Info

Publication number: GB2025380A
Application number: GB7829982A
Authority: GB
Original assignee: Metal Box PLC
Current assignee: Crown Packaging UK Ltd
Priority date: 1978-07-14
Filing date: 1978-07-14
Publication date: 1980-01-23
Also published as: GB2025380B; ZA793421B; AU4872579A

Abstract

A plastics container has a rim portion with a free edge (12) defining the container mouth. At a spacing from the free edge the rim portion has a formation for engagement (at 16) by a complementary formation on a screw-on or snap-on closure (15). Between the free edge and the formation the material of the rim portion is formed with a kink (21). Closure (15) fitted to the container generates an axially directed pressure on the free edge (12) of the rim portion; in response to this pressure kink (21) is partially collapsed into sealing engagement with the closure so as to provide a seal which supplements the seal provided at the free edge. The seal integrity of the bottle is thereby assured. Alternatively, kink (21) may be directed outwardly, Fig. 3 (not shown), or both inwardly and outwardly, Fig. 4 (not shown). The invention has particular application to blow-moulded plastics bottles but may be applied to wide- mouthed plastics containers. <IMAGE>

Description

SPECIFICATION Plastics containers This invention relates to plastics containers such as bottles and tubs.

For economy of material there is a need to use thinner wall thicknesses for plastics containters.

This, however, leads to difficulties with providing an adequate seal for the container mouth to prevent leakage of contents through the mouth when the container is closed by a screw-on or snap-on closure having a closure panel and a peripheral skirt. The difficulties arise because the relative deformability of the container in the neighbourhood of the seal prevents the use of high sealing pressures and with currently available sealing systems tends to result in faulty sealing because of uncontrolled distortion of the container in the sealing area. The present invention seeks to use deformability of a plastics container in the sealing area in a controlled manner, to provide a satisfactory seal with a screw-on or snap-on closure.

In accordance with the invention from one aspect there is provided a plastics container having a mouth-defining free edge on a rim portion thereof, at a spacing from the free edge the rim portion having a formation for engagement by a complementary formation on a skirt of a closure to attach the closure to the container, the rim portion being further formed with at least one kink extending continuously around the rim portion between the formation and the free edge, the arrangement being such that, in use, axially directed pressure on the rim portion applied at the free edge thereof by the closure panel of a said closure fitted to the continer may partially collapse the kink into sealing engagement with the closure.

The kink may be inwardly directed in relation to the container, in which case the closure has a plug portion extending from its closure panel in concentric and spaced relation to the closure skirt for engagement by the kink on the partial collapse thereof. Alternatively, however, the kink may be outwardly directed for engagement with the closure skirt on its partial collapse; the plug portion may then be omitted, but may advantageously be provided to prevent any substantial inward deformation of the rim portion when the kink is engaged.

More than one kink may be provided. In one possible embodiment of the invention the rim portion is formed with two consecutive kinks, one kink being directed outwardly for engagement with the closure skirt, and the other kink being directed inwardly for engagement with a spigot or well disposed in concentric and spaced relation within the skirt.

In accordance with a further aspect, the invention provides a container with a said closure fitted to the container.

In order that the invention may be more fully understood embodiments thereof will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which, Fig. 1 is a detail of the first embodiment, being a sectional view of part of a bottle neck with a screw closure engaged thereon; and Figs. 2, 3, 4 and 5 similarly show the second, third, fourth and fifth embodiments respectively.

Referring now to Fig. 1, a blow-moulded plastics bottle 10 of a suitable plastics material such as high density polyethylene is blowmoulded to have a body (not shown) for containing the bottle contents. The body is closed at its bottom end; at its top end it has a mouth provided by a reduced diameter neck 11, part only of which is shown. The neck 11 forms what may be termed a rim portion for the bottle.

The neck has a circular free edge 12 defining the container mouth. It is formed with a conventional screw-thread formation which projects outwardly from the neck wall 1 3 and with which is engaged a complementary screw-thread deformation created in a cylindrical recess on the inside of the tubular skirt 14 of an injection moulded closure 1 5. The screw-thread formations on the neck and the closure are not shown in detail; they are diagrammatically indicated in combination and denoted by the reference numeral 16.

The closure is formed from a suitable plastics material such as high density polyethylene. It has a plane closure panel 1 7 from the periphery of which the skirt 14 depends, and plug portion in the form of a spigot 1 8 which depends from -the closure panel in concentric and spaced relation to and within the skirt. The spigot is short in relation to the skirt and is frustoconical, tapering outwardly by a small angle (e.g. 1 0) in the direction towards its free bottom edge 1 9. It will be seen that, in combination with the skirt, the spigot defines a downwardly open channel 20 around the closure on the under-side of the closure panel.

The neck wall 13 is cylindrical with the exception of a kink 21 with which it is formed between its free edge 12 and the screw-thread formation provided on the bottle at 1 6. The kink is directed inwardly of the neck 11 and is formed by opposed frustoconical parts 2 1A, 218 joined at an elbow 22. The parts 21A, 21B, are inclined at equal angies to the central axis (not shown) of the container and are of equal length. The kink extends continuously around the neck 11, with substantialiy the same constant material thickness as the remainder of the neck wall.

Figure 1 shows the closure 1 5 when screwed fully home on the bottle. As can clearly be seen from the drawings, the upper end of the neck 11 including, in particular, the free edge 12 and the kink 21, is then received within the downwardly facing channel 20 on the underside of the closure panel 1 7. The closure panel within the channel 20 bears down on the free edge 1 2 to generate on the kink 21 a pressure which, as indicated by the arrow A, is directed axially of the container.

The material thickness of the neck wall 13 is such that the neck wall is readily deformable; typicaily, for example, the material thickness is .5 mm on a neck diameter of 34 mm. By virtue, therefore, of the inclinations of its component parts 21A, 21B, the kink 21 is caused by the axial pressure exerted by the closure panel to deform inwardly by bending of the wall material at the ends of the parts 21A, 218 and thereby to engage the spigot 18 at the elbow 22. This engagement is continuous around the neck so as to provide a seal preventing escape of the bottle contents which may for example, be a fruit juice cordial. This seal is supplementary to, and in serial relation with, the further continuous seal which is provided at the engagement of the free edge 1 2 with the closure panel 1 7 as described above.

Any tendency of the neck wall 13 to deform outwardly, as a result of the radial forces generated at the kink 21 or otherwise, is resisted by engagement of the neck wall with the interior surface of the closure skirt 14. Inward deformation of the neck wall other than at the kink is resisted by the circularity of the neck wall itself.

It will thus be seen that the arrangement shown and described provides a multiple seal arrangement which uses the deformability of the bottle neck to provide sealing and of which the seal integrity is, in generai, increased the further the closure is screwed onto the bottle.

Although not apparent from the drawing, a lower limiting position is provided for the closure, for example by axial engagement of the closure and the bottle at the screw thread formations 16 or at the free edge (not shown) of the closure skirt 14. This limit ensures that the seal integrity of the closure cannot be impaired by over-screwing of the closure. Fig. 1 shows the closure in the limiting position; from Fig. it will be understood that the dimensions and inclinations of the component parts 21% 21B of the kink 21 are so chosen in relation to the radial width of the closure channel 20 that the kink is then only partially collapsed.In this way it is ensured that the sealing engagement of the neck 11 with the closure 1 5 at the free edge 12 and at the elbow 22 is resilient in nature, despite substantial manufacturing tolerances which may be present in the neck/and or the closure.

Application of the closure to the bottle neck 11 is conventionally effected manually or by machinery. The initial location of the closure on the bottle prior to screwing-up is assisted by the spigot 18 the free bottom edge 19 of which rides down the upper frustoconical part 21A of the kink 21 to correct any radial misalignment or tilting of the closure on the bottle neck. The small axial inclination of the spigot is provided in order to reduce angle included between the spigot and the lower frustoconical part 218 of the kink 21. The purpose of this reduction is the same as for the modification now to be described with reference to Fig. 2.

Fig. 2 shows the second embodiment of the invention to be similar to the first embodiment in many respects, and the same reference numerals as before are accordingly used to indicate like or analogous parts.

The arrangement of Fig. 2 differs from that of Fig. 1 in that the frustoconical parts 21A, 21B of the kink 21 are no longer of equal length and equally inclined; instead, the upper part 21A is longer than the lower part 21B but inclined at a smaller angle to the bottle axis. Such an arrangement generates higher sealing forces at the elbow 22 than are generated in Fig. 1 for the same axial pressure A; the arrangement is, however, less able to accommodate manufacturing tolerances than the Fig. 1 arrangement.

Fig. 3 shows the third embodiment to have a kink 21 which is outwardly directed, in contrast to those of the first two embodiments which are inwardly directed. The elbow 22 of the kink therefore engages the closure skirt 14. A spigot 1 8 is again provided; it is arranged to engage the interior of the bottle neck so as by reacting the radially inward forces generated on the kink to prevent any substantial inward deformation of the bottle neck in the neighbourhood of the kink. In a modification of the Fig. 3 arrangement, however, the spigot 18 is omitted and the circularity of the neck 11 is relied upon to resist inward deformation. Such an arrangement enables a plane sealing diaphragm to be secured over the bottle mouth.

In Fig. 3 the bottom free edge 19 of the spigot is angled downwardly and inwardly to assist initial location of the closure on the bottle neck. In order to enable the screw threads on the closure to clear the kink 21 when the closure is initially applied the screw threads on the bottle are formed on a collar 25 projecting integrally from the neck wall 13.

Fig. 4 shows an embodiment in which two kinks, donoted 121 and 221,are provided. The kink 121 is directed outwardly for engagement with the closure skirt 14; the kink 221 is directed inwardly for engagement with the spigot 1 8. The kinks share a common frustoconical part 21 C extending between their two elbows 122 and 222. The upper kink 121 is otherwise formed of a frustoconical part 21A, the lower kink 221 likewise having afrustoconical part 21B. It will be seen that, in operation, when the closure is screwed home and an axial pressure A is exerted as before on the free edge 12 of the neck 11, the two kinks act back-to-back to make individual sealing engagement one with the closure skirt 14 and the other with the spigot 18. Three seals in series relation are thus available to prevent escape of contents from the bottle.

A possible variation of each of the embodiments of Figs. 1 to 4 is illustrated in Fig. 5 which shows it in relation to the first embodiment (Fig. 1); it is to be understood, however, that the embodiments of Figs. 2, 3 and 4 may be likewise modified in this way.

In the embodiment of Fig. 5 the plug portion, formerly constituted by the spigot 1 8, is now in the form of a well closed at its bottom end but open at its top end, the closure panel being correspondingly annular rather than a plane, unbroken disc as before. In Fig. 5 the closure panel is denoted 17'; the well is generally denoted by the reference numeral 18', its bottom being denoted 26.

Axially of the bottle, the well bottom 26 corresponds in position to the elbow 23; it is thus in the optimum position for the well 1 8' to react the radial forces exerted by the kink 21.

Within the scope of the present invention many variations of the arrangements shown and described are possible, and the invention is not to be considered as being limited in application to screw-on plastics closures; it may have application to snap-on closures and to closures which are other than circular and/or of a metal rather than plastics material. Kink formations may be used other than those comprised of two opposed frustoconical parts as particularly described. Two or more kinks, preferably consecutive, may be provided if desired; they may all be inwardly or, alternatively, outwardly directed, but preferably are alternately inwardly directed and outwardly directed as in the embodiment of Fig. 4.

Although of particular advantage for thinwalled containers because of their inherently deformable nature, the invention may be applied to thick-walled, essentially rigid, containers if the necessary deformability at the kink or kinks is introduced by local thinning or otherwise weakening of the plastics material. The container side wall in which the one or more kinks are provided may accordingly be essentially rigid or deformable; moreover, it may be a laminated structure including paper and/or metal foil.

The invention is not limited, as particularly described, to blow-moulded bottles having reduced-diameter necks. Thus it may be applied to plastics containers (injection-moulded or thermoformed) in the form of tubs of which the side wall tapers outwardly and upwardly from a base to a rim portion having a free edge which defines a large aperture mouth for the container.

In accordance with the invention the rim portion has a formation for engagement by a corresponding formation on a snap-on closure, and one or more continuous deformable kinks extending round the rim portion between this formation and the free edge.

Claims

1. A plastics container having a mouth-defining free edge on a rim portion thereof, at a spacing from the free edge the rim portion having a formation for engagement by a complementary formation on a skirt of a closure to attach the closure to the container, the rim portion being further formed with at least one kink extending continuously around the rim portion between the formation and the free edge, the arrangement being such that, in use, axially directed pressure on the rim portion applied at the free edge thereof by the closure panel of a said closurefitted to the container may partially collapse the kink into sealing engagement with the closure.

2. A plastics container according to claim 1, having a said kink which is inwardly directed for engagement with a plug portion of the closure.

3. A plastics container according to claim 1 having a said kink which is outwardly directed for engagement with the said closure skirt.

4. A plastics container according to claim 2, which includes a further said kink consecutive with the first, the further kink being outwardly directed for engagement with the said closure skirt.

5. A plastics container according to any preceding claim, wherein the or each said'kink is formed of two frustoconical parts joined at an elbow at which to engage the said closure.

6. A plastics container according to claim 5, wherein the two frustoconical parts are of equal length and equally inclined.

7. A plastics container according to claim 5, wherein the two frustoconical parts have differing lengths.

8. In combination, a plastics container as claimed in claim 2 and a said closure fitted thereto, the closure skirt closely surrounding the rim portion so as to resist substantial outward deformation thereof.

9. In combination, a plastics container as claimed in claim 3 and a said closure fitted thereto.

10. The combination claimed in claim 9, wherein the closure has a plug portion disposed in concentric and spaced relation to and within the closure skirt, the rim portion closely surrounding the plug member so as to be restrained thereby against substantial inward deformation.

11. The combination claimed in claim 10, wherein the plug portion has a terminal free edge which is inclined in the sense to assist initial location of the plug member within the rim portion.

1 2. The combination claimed in any claim of Claims 8, 10 and 11 , wherein the plug portion comprises a spigot extending from attachment to the closure panel at one end to a terminal free edge at the other.

1 3. The combination claimed in claims 8 or claim 10, wherein the plug portion comprises a well having a tubular side wall depending from the closure panel, the side wall being closed at itp end remote from the closure panel but having its other end open.

14. A plastics container having a rim portion substantially as hereinbefore described with reference to Fig. 1, or Fig. 2 or Fig. 3, or Fig. 4, or Fig. 5 of the accompanying drawings.

1 5. A plastics container and closure combination, substantially as hereinbefore described with reference to Fig. 1, or Fig. 2, or Fig.

3, or Fig. 4, or Fig. 5 of the accompanying drawings.