GB2161797A

GB2161797A - Pre-threaded container closure

Info

Publication number: GB2161797A
Application number: GB08418304A
Authority: GB
Inventors: Kenneth Martin Sinnott; John Richard Knight; Geoffrey Richard Thwaites
Original assignee: WR Grace and Co
Current assignee: WR Grace and Co
Priority date: 1984-07-18
Filing date: 1984-07-18
Publication date: 1986-01-22
Also published as: EP0168982A1; AU4480985A; ZA854925B; AU586429B2; NZ212593A; JPS6133949A; GB8418304D0; GB2161797B

Description

1

SPECIFICATION

Pre-threaded container closure GB 2 161 797 A 1 The present invention relates to a pre-threaded container closure, of the type serving as a screw cap for 5 engagement on a neck of the container, for example the neck of a glass bottle.

Pre-threaded container closures are known in two main forms, the metal screw cap and the injection moulded plastics screw cap. Traditionally similar gasket designs have been used for these two kinds of pre-threaded closures, as for example in Published United Kingdom Patent Application No. 2,116,529A and in WO 82/02182, both disclosing plastics caps with gaskets aimed at achieving high compression of 10 the gasket material around the outside corner of the bottle neck rim.

This "corner seal- placement of the gasket has been evolved after many years of development with luminium,bottle caps and has been found to give satisfactory protection against the tendency of the cap to "dome" when subjected to high internal pressures. This doming of the cap end panel has the effect of lifting the cap top panel upwardly at the centre and hence also upwardly to lesser degrees at stations 15 radially outwardly of the centre, but the gasket compression on the outside corner is virtually unaffected, and may even be increased slightly, as a result of this doming which is a known phenomenon in both aluminium pre-threaded caps and moulded plastics pre-threaded caps. The "corner seal" placement is thus highly advantageous with a good quality glass bottle.

However, problems arise with regard to the quality of the-glass finish, firstly with regard to the diffi- 20 culty of ensuring close tolerances on the bottle neck radius with the result that some bottles may have differing internal diameters and to some extent differing external diameters, and secondly with regard to the use of returnable bottles where a re-used bottle may show signs of damage sustained during a pre vious "trip" (this damage manifesting itself as roughening of the outside corner of the glass, or chips on the glass, or even small cracks which have not been detected during the quality control inspection of 25 returned bottles).

With a glass bottle neck on the limits of its radius tolerance, the sealing performance will be disadvan tageously affected because the gasket is intended to achieve a desired compression against the outside corner of the glass bearing in mind the expected gap between the outside corner and the internal surface of the cap skirt, so a larger than normal outside diameter of the bottle runs a risk of jamming of the cap 30 during screwing-on, and a smaller than normal outside diameter to the cap can result in inadequate gas ket compression for sealing.

The problem of damage to the outside corner manifests itself as increased friction between the gasket and the neck during screwing-on and hence either the use of a fixed torque applicator will result in inad equate axial compression of the gasket for sealing, or alternatively if the cap is screwed on tight enough 35 to ensure the correct gasket compression the application torque, and hence the removal torque, will be excessively high and unacceptable for practical considerations of the need for the bottle to be. opened, without the use of special tools, by the consumer. The problem of high application torque has been tac kled by ensuring lubrication between the gasket and the bottle as in European Patent Application 84302637.8- (Publication The problems of bottle diameter variation and of neck damage are not so important with regard to the so-called "roll-on" closure where the blank is supplied without threads and the threads are then rolled onto the rigid bottle neck and at the same time an axial loading and radial contraction of the corner of the cap (the "reform" step) are used to shape the cap to fit the individual bottle. Further- more, the avoidance of any rotation of the cap during the application process has the advantageous result that the 45 gasket composition will be pressed into any imperfections on the bottle neck rim and achieve the desired seal. With pre-threaded caps, for the reason stated above, these problems are considerable and it is an object of the present invention to provide for sealing of containers whose neck rims are damaged ano/or of non-standard size.

Accordingly, the present invention envisages the surprising step of achieving a seal which requires no 50 gasket composition in contact with the outer corner of the container rim, and instead employs a particu lar profile to the container, arid/or the gasket, and/or the closure to provide for adequate sealing action on the inner corner of the container neck as the closure is screwed-on.

One aspect of the present invention provides a process of closing a container having an externally threaded neck, comprising: taking a container closure having an end panel, an internally threaded skirt, 55 and a separately formed gasket; and screwing that pre-threaded closure onto the container neck to close the containw neck, to achieve sealing contact of the end of the neck rim without contact of the material of said gasket against the outer corner of the bottle neck rim.

A second aspect of the present invention provides a pre-threaded container closure having a separately formed gasket therein, the gasket having a surface configuration such that its surface is further from the 60 median plane of the end panel of the closure at a radially inner location than it is at a radially outer location, whereby the gasket seals against the inner corner of the container neck rim without contact of gasket composition against the outer corner of the container neck rim.

Yet a third aspect of the present invention provides a pre-threaded container closure having an inter- nally threaded skirt, an end panel, and a separately formed gasket, wherein the end panel includes a rib 65 2 GB 2 161 797 A 2 embedded in the gasket to generate localised increased compression of the gasket material in an annular region thereof adjacent to the location of the internal corner of the neck rim of a container on which the closure is to be used, soAhe gasket seals against the internal corner of the container neck rim without contact between the gasket and the outer neck rim corner.

A fourth aspect of the invention provides in combination, a container having an externally threaded neck, and a closure having an end panel joined to an internally threaded skirt and including a separately formed gasket on the end panel, wherein the gasket has a surface arranged to contact the container neck, upon closing of the container, and the gasket surface is so shaped and positioned in relation to the con tainer neck that the gasket composition forms a seal with the end of the container neck rim without con- tact of gasket composition with the outer corner of the container neck rim.

A fifth aspect of the invention provides in combination, a container having a threaded neck, and a closure having an end panel joined to an internally threaded skirt to engage the container neck. wherein the end of the container neck is shaped to encourage movement of the gasket composition rad i ally inwardly of the end panel during closing of the container using that closure, to effect a seal on the inside corner of the container neck.

Finally, the invention provides a closed container having been _closed by the method of the first aspect of this invention.

The step of relying on sealing at the inside corner of the container neck is, as indicated above, a very surprising one to take because of the natural expectation that the "doming" of the cap will have the effect of relaxing gasket compression where the compression arises at the inside corner, despite the fact 20 that gasket compression at the outside corner is substantially unaffected by doming. However, we have found that the quality of the seal achieved using this "inside corner sealing" placement of the gasket does not give rise to unacceptable problems through "doming" but does overcome the independent problems due to wide tolerances on the container neck diameter, including the internal diameter, and damage of the rim of a returnable glass container on a previous trip (because most of the damage will 25 be experienced on the outside corner and the inside corner is therefore relatively unharmed).

In order that the present invention may more readily be understood the following description is given, merely by way of example, with reference to the accompanying drawings in which.

Figure 1 shows a diametral cross-section of the closure, with a partly sectional illustration of the con tainer neck, in this case a glass bottle neck to which the cap is to be fitted, but illustrates the prior art 30 form of cap with a -corner seal" placement of the gasket; Figure 2 is similar to Figure 1 and shows a first embodiment of the container closure in accordance with the present invention, with the gasket just in contact with the container neck but before any appre ciable compression of the gasket during the screwing-on process; Figure 3 is a view, similar to Figure 2, but showing a different embodiment of cap and gasket in accordance with the invention; Figure 4, again similar to Figure 2, shows a still further embodiment of the closure, but this time with the container neck shown totally in section; and Figure 5, again similar to Figure 1, shows a view of a further embodiment of the present invention.

The prior art form of cap 1 shown in Figure 1 has a gasket 2 positioned in the vicinity of the corner 40 between the cap end panel 3 and the cap skirt 4 so that, as the cap 1 is screwed onto a bootle neck 5, the gasket 2 becomes pressed into sealing contact with the outside corner 6 of the bottle neck. As explained above, imperfections in the glass and in particular damage caused by previous "trips" of a returnable bottle, cause problems with regard to this corner placement which is conventional in the art.

Figure 2 shows a first embodiment of a cap, again referenced 1, in accordance with the present inven- 45 tion. In this case the gasket 2 is moulded in a recess whose floor 8 slopes in a direction such that it is further from the median plane 3a of the end panel 3 of the cap at the radially inner portion near an inner gasket-containment bead 9 than it is at its outer portion near the corner between the end panel 3 and the skirt 4. The free surface of the gasket which contacts the bottle neck rim 5 as the bottle is closed, also slopes in the same way in relation to the median plane of the end panel 3.

In this case the gasket 2 is formed by being flowed-in to occupy the space defined between the inner gasket-containment bead 9 and an outer gasket-containment bead 10, and the gasket composition adopts the illustrated profile upon cooling.

As the cap 1 is screwed onto the bottle neck 5 the gasket 2 initially makes contact with the top of the bottle neck rim but the inclination of the surface of the gasket 2 is such that the gasket composition moves down onto the inner corner 7 of the bottle neck to provide the required "inner corner seal" action.

In this case the slope of the floor 8 of the gasket-receiving groove of the cap, and the shape of the gasket 2 itself, both contribute to ensure the desired---innercorner seal" action.

Figure 3 shows an alternative form of the gasket in which the gasket 2 may be moulded to adopt the distinctly toroidal configuration, or may be formed by virtue of the high viscosity of a flowed- in compo- 60 sition, and is held in the flat-bottomed gasket-receiving groove by means of the undercut of the inner gasket-containment bead 9 of Figure 2, and an undercut 11 in place of the outer gasket- containment bead 10. The slope of the surface of the gasket 2 is entirely due to the thickness of the gasket and is such that as the bottle cap is screwed down onto the bottle neck, the shape of the gasket 2 and the shape of the bottle neck 5 co-operate to shift gasket composition down towards the inner corner 7 of the glass 65 3 GB 2 161797 A 3 neck rim. Here the neck configuration and the gasket shape co-operate to give the desired "inner corner seal" action.

Figure 4 illustrates a further form of cap in accordance with the present invention and in this case the gasket 2 is a pre-formed disc of uniform thickness which has been inserted into the cap 1 so that it sits on an annular projection 12 having a slope which causes the undersurface 2a of the gasket to adopt a -5 configuration similar to that of Figure 2 in that it is capable of co- operating with the glass bottle neck to cause gasket compression and contact of the gasket material at the inner corner 7 of the bottle neck. In this case it is the shape of the cap which gives the desired configuration for "inner corner seaV action.

Finally, Figure 5 shows a further flowed- in gasket 2 in a cap 1 having a rib 13 formed in the floor of the gasket-receiving groove between the inner gasket-containment bead 9 and the outer gasket-contain- 10 merit bead 10 analogous to those of Figure 2.

Although in this case the gasket has a free surface which has a slight inclination in the same direction as that shown in Figures 2 and 4, this embodiment relies heavily on the rib 13, embedded in the gasket, to ensure that there will be higher compression of the gasket material between. the rib 13 and the end face of the bottle neck near the inner corner 7 of the neck rim, giving the desired result of high gasket 15 compression at the inner corner and some shifting of composition around onto the inner corner for sealing thereon.

Yet a further possibility (not illustrated) is for the gasket to have a relatively flat configuration and for all of the profiling to give the desired "inner corner seaV action to be derived from the shape of the glass finish itself.

It will of course be understood that each of the embodiments of Figures 2 to 5 has a configuration in which there is contact of the gasket with part of the end face of the bottle neck but pronounced sealing contact around the inner corner 7 of the bottle neck without, in any of these embodiments, any substantial -contact between the gasket 2 and the outer corner (referenced 6 in Figure 1) of the neck rim. Hence if there is any roughening of the outer corner 6, or the evidence of chipped regions of that corner, there 25 will be no appreciable increase in application torque and removal torque.

Example

In order to illustrate the fact that the sealing performance is independent of the quality of the glass finish, tests were carried out using 28 mm plastics caps on readily available samples of returnable glass 30 bottles. Ten examples of the bottle were used, and the second column illustrates the condition of the bottle, e.g. "chipped and cracked", "rough", and "OK".

The hot melt composition used for forming the gasket was placed in two alternative placements in identical caps, one corresponding to the "comer seal" action illustrated in Figure 1, and the other corre- sponding to the "Inner corner seaW action typical of Figures 2 to 5. The venting pressure values as tested 35 by means of an Owens Illinois "Secure Seal Tester" are set out in the third column for the "corner seal" placement of Figure 1 and in the fourth column for the "inner corner seal" placement in accordance with the present invention. The venting pressure values quoted are measured in pounds per square inch but with the "S.L" value measured in KPa shown in brackets alongside the imperial value.

The bottom line of the table quotes the average film weight of the gasket and shows that a slight re- 40 duction in the film weight was achieved with the "inner corner seal" placement shown in the fourth col umn despite the fact that the venting pressure results were more consistent in that case.

TABLE 45

Bottle Glass Comer Inner Comer No Condition 1 OK 150+0034+) 150+0034+) 50 2 -OK 150+0034+) 150+0034+) 3 OK 150+ (1034+) 150+(1034+) 4. Chipped & Cracked 0 150+(1034+) Rough 65(448) 150(1034) 6 OK 150(1034) 150+(1034+) 55 7 OK 75(517) 150(1034) 8 Numerous chips 0 150+(1034+) 9 OK 150+(1034+) 150+(1034+) OK 150+(1034+) 150+(1034+) 60 Average 252 246 Film Wt.(mg) 4 GB 2 161 797 A 4 As can be seen from the results quoted, bottles numbers 4 and 8 were so badly damaged that there was no seal achieved. with the "corner seal" placement of Figure 1. Furthermore, bottles 5 and 7 achieved only a low venting pressure result (bearing in mind that venting. pressures in excess of 150 Ibl in2 (1034 kPa) are considered acceptable for pressure holding applications.

With the damaged samples numbers 4 and 8 with which no sealing was possible on the "Corner seal" placement, acceptable venting pressure values were obtained with the "inner corner seal" placement, and with damaged sample number 5 where only a partially effective seal was obtained on the "corner seal" placement a venting pressure value equivalent to the limit of acceptance was obtained. With the other samples numbers 6 and 7, on which values which were not clearly above the limit of acceptance were achieved with the "corner seal" placement, in each case the values are improved in the "inner cor- 10 ner seal" placement of the gasket.

It will of course be understood that the gasket can be formed by any one of several different methods, many of which are illustrated in the drawings.

For example, a hot melt composition in accordance with our European Patent Application Nos.84302637.8 and 84302638.6 (Publications Nos. and) may be poured into the gasket- receiving15 groove of the pre-formed cap and distributed throughout the groove by spinning of the cap whereupon the cooling of the composition causes it to adopt the desired configuration of the finished gasket. Such-a gasket may, if desired, be formed using the method of our British Patent No. 2,051,660B relating to mi crowave heating of the plastisol to form the gasket with separate non- microwave heat[ng of the closure to enhance uniformity of heating of the plastisol.

The flowed-in gasket may, if desired. be of a foamable composition so that the gasket material can be caused to foam upon heating, for example as disclosed in published British Patent Application No.

2,116,473.

Another possibility is for a plastics composition to be moulded, as necessary to produce the gasket of Figure 3, and to effect this the composition may be placed in the cap in molten form and then moulded to form the gasket. The composition may be as disclosed in our British Patents Nos. 1,112,023, 1,112,024, 1,112,025.

The configuration of Figure 3 may alternatively be formed by flowing in a high viscosity thermoplastic melt whose viscosity will then cause the resulting bead of the melt to adopt the Figure 3 configuration which it will retain on cooling.

Yet a further possibility illustrated in Figure 4 is for the gasket to be a pre-formed disc or annulus, either flat or profiled, which is inserted in the moulded cap and retained in the cap by suitable means (not shown in Figure 4).

As indicated above, we have surprisingly found that if the natural prejudice against "inner corner seal action is overcome the use of such a sealing action results in the cap which has a much better sealing 35 performance with damaged bottles that can be achieved with the conventional---comer seal" action of Figure 1 (see the third column in the Table). When the cap domes under internal pressure, the gasket is understood to lift slightly but the resilience of the gasket is such that it is nevertheless able to keep the bottle sealed even after such deformation of the cap end panel.

Claims

1. A process of closing a container having an externally threaded neck, comprising:

taking a container closure having an end panel, an internally threaded skirt, and a separately formed gasket; and screwing that pre-threaded closure onto the container neck to close the container neck, toachieve sealing contact of the end of the neck rim without contact of the material of said gasket against the outer corner of the bottle neck rim.

2. A process according to claim 1, wherein the sealing action occurs mainly on the internal corner of the container neck rim.

3. A process according to claim 2, wherein the achievement of inner corner sealing is due to the con- 50 figuration of the gasket.

4. A process according to claim 2 or 3, wherein the achievement of the inner corner seal action is by virtue of the shape of the closure.

5. A process according to claim 3 or 4, wherein the gasket has a container-contacting surface which is further from the median plane of the closure end panel at a radially inner part than at a radially outer -55 part thereof.

-

6. A process according to any one of claims 2 to 4, wherein the closure includes an up-standing rib embedded in the gasket substantially in register with the internal corner of the container neck rim to increase compression of the gasket in the vicinity of the inner corner of the container neck rim.

7. A process according to any one of claims 2 to 6r wherein the achievement of the inner corner seal 60 action is due to the configuration of the container neck rim.

8. A process of closing a container, substantially as hereinbefore described with reference to, and as illustrated in, Figures 2 to 5 of the accompanying drawings.

9. A container closed by the process of any one of claims 1 to 8.

10. A pre-threaded container closure having a separately formed gasket therein, the gasket having a65 GB 2 161 797 A surface configuration such that its surface is further from the median plane of the end panel of the clo sure at a radially inner location that it is at a radially outer location, whereby the gasket seals against the inner corner of the container neck rim without contact of gasket composition against the outer corner of the container neck rim.

11. A closure according to claim 10. wherein the closure has a groove to receive the gasket and the 5 groove has a floor configured such that at a radially inner portion it is further from the median plane of the end panel of the closure than it is at a radially outer portion.

12. A closure according to claim 10, wherein the gasket has a thickness which varies from a maxi mum value at said radially inner location to a minimum value radially outwardly thereof.

13. A closure according to claim 10, wherein the gasket is a pre-formed member inserted into the 10 closure.

14. A closure according to claim 13, wherein the pre-formed gasket is inserted on a part of the closure end panel having a greater spacing from the median plane of the closure end panel at said radially inner location and a smaller said spacing radially outwardly thereof.

15. A closure according to claim 13 or 14, wherein the pre-formed member is of uniform thickness. 15

16. A closure according to any one of the preceding claims, wherein the closure end panel includes an upstanding rib adjacent said radially inner portion of the gasket for inducing localised increased compression of the gasket during container closing.

17. A pre-threaded container closure having an internally threaded skirt, an end panel, and a sepa- rately formed gasket, wherein the end panel includes a rib embedded in the gasket to generate localised 20 increased compression of the gasket material in an annular region thereof adjacent to the location of the internal corner of the neck rim of a container on which the closure is to be used, so the gasket seals against the internal corner of the container neck rim without contact between the gasket and the outer neck rim corner.

18. In combination, a container having an externally threaded neck, and a closure having an end panel joined to an internally threaded skirt and including a separately formed gasket on the end panel, wherein the gasket has a surface arranged to contact the container neck, upon closing of the container, and the gasket surface is so shaped and positioned in relation to the container neck that the gasket com position forms a sea] with the end of the container neck rim without contact of gasket composition with the outer corner of the container neck rim.

19. A combination according to claim 18, wherein the gasket has a parttoroidal shape with said sur face defined as the part-toroidal surface of the gasket.

2.0. In combination, a container having a threaded neck, and a closure having an end panel joined to an internally threaded skirt to engage the container neck, wherein the end of the container neck is shaped to encourage movement of the gasket composition radially inwardly of the end panel during 35 closing of the container using that cap, to effect a seal on the inside corner of the container neck.

21. A combination according to claim 20, wherein the container neck rim has an end surface which slopes in relation to the axis of the container neck, such that that end surface has a radially outer part which is further from the interior of the container, measured in a direction axially of the container neck, than is the radially inner part of said end surface.

22. A combination according to claim 21, wherein the gasket has a surface which is inclined in the same direction as said end surface of the container neck rim.

23. A combination according to claim 22, wherein said closure has a surface inclined in a manner similar to that of the end surface of the bottle neck rim for imparting the desired surface configuration for the gasket.

24. A container closure substantially as hereinbefore described with reference to, and as illustrated in, Figure 2, or Figure 3, or Figure 4, or Figure 5, of the accompanying drawings.

Printed in the UK for HMSO, D8818935, 12,185, 7102.

Published by The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.