GB2189776A

GB2189776A - Threaded container and closure therefor

Info

Publication number: GB2189776A
Application number: GB08610570A
Authority: GB
Inventors: Geoffrey Alan Ryder
Original assignee: WR Grace and Co
Current assignee: WR Grace and Co
Priority date: 1986-04-30
Filing date: 1986-04-30
Publication date: 1987-11-04
Also published as: JPS6365A; ZA872411B; AU7119887A; EP0244065A3; GB8610570D0; EP0244065A2

Abstract

A threaded container has non-overlapping thread portions 4a and 4b of a multi-start thread such that at the parting line 7 of the external mould parts for the moulded container 1 there is a zone in which the generatrices of the container rim do not intersect any of the thread portions of the multi-start container external thread. This facilitates parting of the external mould parts of the container. Preferably the container rim is closed by a closure having an internal multi-start thread comprising thread portions which are overlapping such that in every position of the generatrix of the closure skirt the generatrix intersects a thread portion of the skirt. <IMAGE>

Description

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SPECIFICATION

Threaded container and closure therefor

5 The present invention relates to a threaded container, and to a closure for such a container, and in particularthe container may be a jar of glass or of relatively rigid plastic material.

When moulding threaded containers of relatively 10 rigid material such as glass or hard plastics (for example acrylonitrile-butadiene-styrene or polyethylene terephthalate, a difficulty arises in the moulding of the threads which are intended to follow a helical path around the container rim whereas the 15 threaded rim is formed by moulds designed to separate by movement perpendicularto the axis of the container rim.

One commonly used solution to this problem has been to provide the threads, where they intersect the 20 parting line of the mould parts, with a region in which the helical path of the thread portion is deformed to a short section which extends with zero pitch around the container rim so that at this point where the mould parts part from one anothertheir 25 movement is parallel to the localised extent of the thread portion. However, while this system has been used successfully on glass jars intended for metal caps of the "lug cap" type it has not been possible to provide a helically threaded cap,forexample 30 moulded of plastic material, to give adequate engagement with such a distorted container rim thread. As the threaded cap is screwed down there will beatendencyforonlythe lead-in part of the rim thread up to the parting line location to engagethe 35 threads of the cap. This restriction of the length of thread portion overwhich thread-to-thread engagement occurs also has the disadvantage that due to the stresses in the cap resulting from the screwing down forces being concentrated at these 40 thread-to-thread contact zones the cap skirt tends to bulge outwardly at locations away from the contact zones, and the cap assumes a non-circular configuration, by virtue of the elasticity of the cap skirt and tends to leak and/or to give an 45 unsatisfactory appearance. This tendency of the cap to bulge is exacerbated if the cap is heated, for example, if the container afterthe cap has been closed on it is pasteurised orsterilised. Injection of steam into the head space of the container whilethe 50 cap is being closed onto the container will also heat the cap and thereby increase the tendency to bulge.

It is an object of the present invention to overcome the above-mentioned deficiencies.

Accordingly, the present invention provides a 55 moulded threaded container having a rim provided with a multi-start thread, the thread consisting of at least two non-overlapping thread portions arranged such that at least at the parting line of the container mould parts the container rim generatrix fails to 60 intersect any of the container rim thread portions at least in the main extent of the thread away from the thread run-out portions.

A more detailed aspect of the present invention provides the combination of a threaded moulded 65 container and a threaded closure, wherein the thread of the container is a multi-start external thread on a cylindrical container rim and the thread of the closure is a multi-start internal thread, wherein the thread portions of the container rim are non-overlapping, wherein the container rim mould parting lines occur where said container rim thread portions are non-overlapping, and wherein the thread portions of the closure skirt are mutually overlapping such that at all positions around the closure skirt the generatrix of the closure skirt intersects at least one of the thread portions of the closure skirtthread.

In orderthatthe 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 is a side elevational view of a threaded container in accordance with the present invention;

Figure2 is a development view showing one start of the containerthread and a corresponding start of the thread of a closure intended to be screw-fitted on the container of Figure 1;

Figure 3 is a detail view of an alternative embodiment of container having a closure attached;

Figure 4 is a view of yet a further embodiment of container having a closure attached; and

Figure 5\s a view of a still further modified form of container with a further modified form of closure equipped with a tamper-evident feature.

Referring nowto the drawings, Figure 1 shows a container in theform of a jar 1 having a body 2 and a rim 3 at the open end.

Around the rim 3 is a two-startthread having thread portions 4a and 4b. Below the cylindrical rim 3, and between it and the jar body 2 is a transfer groove 5 designed to allow a hot just-moulded container 1 to be lifted from the moulding station to a cooling station by means of transferforks well known in the glass blow moulding industry.

As shown in Figure 1, the thread portions 4a and 4b are non-overlapping, and define between them a region 6 in which the mould parting line7forthe container-forming mould arises. In this particular case, given a two-startthread 4a, 4b, the mould can be a simple two-part external mould which has opposed mould portions which advance towards and away from the parting plane defined by the line 7 of Figure 1 and extending perpendicularto the paper in Figure 1.

At the parting line 7 where the two mould parts come into engagement, there is no helically extending thread part of the container rim 3 and hence no problem arising from purely tangential movement of the mould perimeters at that location.

Conventionally a multi-start thread on a container rim hasthevariousthread portions overlapping, i.e. there is no generatrix of the container rim which is not intersected by a part of the thread. For example a fourstartthread has four regularly staggered thread portions which each extend over more than a quarter of the neck rim circumference. The present invention differs from such constructions in deliberately allowing for non-overlapping of the threads, at least in the main extent of the thread away from the thread run-out portions, and preferably even avoiding

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overlap of the thread run-out portions. Indeed,as shown in Figure 1, the thread run-out portions stop short of one another so as to define, between thetwo thread portions 4a and 46, the above-mentioned 5 zone 6 in which the neck rim generatrix (not shown but which would be parallel to the parting line 7)

does not intersect either of the thread portions 4 a and 46.

Figure 2 illustrates a still furtherfeatu re of the 10 present invention and is a development view of the container rim 3 of Figure 1 and shows only the thread portion 4a of Figure 1. Figure 2 also shows a corresponding thread portion 8 a of the multi-start internal thread of a container closure, such as a cap, 15 to fit on the jar 1 ofFigurel and it is clearfrom Figure 2 thatthe closure internal thread portion 8a is considerably longer than the container rim external thread portion 4a. In this particular case the closure thread portion 8a is sufficiently long forthere to be 20 overlap of the thread portions of the closure, and in this case the overlap issuch that the main thread portions apart from the thread run-out portions are fully overlapping. In otherwords every generatrix of the closure intersects at least one portion 8a or 86 of 25 the closure skirt interior.

The advantage of the overlapping configuration of the closure internal thread portions will now be explained:-

If we considerthe situation in Figure 1 where an 30 internally threaded closure is screwed onto the cylindrical rim 3 of the jar 1, the screwing down forces result in the skirt of the cap being under tension, as a result of which the threads of the closure tend to ride-up over the threads of the jar. If 35 there is an internal pressure in the closed jar or if an internal pressure results when the closed jaris subjected to a heat treatment operation, such as a pasteurisation orsteriiisation,this internal pressure will further increase the tendency of the threads of 40 theclosureto ride-up those of the jar. Upward movement will be resisted by the engagement of the upper side faces of the closure thread portions 8a and 86 with the underneath sidefaces of the container rim thread portions 4a and 46. Because of 45 the generally tapering cross-section of the container threads 4a and 46 (see the right and left extremities of the illustrated rim 3 of Figure 1) and the corresponding generally tapered configuration of the thread portions 8a and 86 of the closure, the 50 closure threads will tend to ride up overthe containerthreads causing the closure to expand radially in the regions where there is thread-to-thread engagement between the closure and the container.

55 This distortion of the closure is possible because of the relatively flexible nature of the plastic closure which may, for example, be formed of polyethylene, polypropylene, ethylene-propylene copolymers, polyacetals, polycarbonates, polyesters or 60 polystyrene, or mixtures of these. The closure may also include a filler such as calcium carbonate talc, china clay or glass fibres. These fillers would be incorporated into the material of the closure to improve theirrigidityand mechanical strength 65 and/orto renderthem less permeable to gases and watervapour.

The tendency for outward bulging of the closure where there is thread-to-th read engagement between the closure and the jar rim isfacilitated by 70 the existence of the region 6 at which all generatrices of the jar neck rim 3 fail to intersect a jar rim thread portion 4a or46, since this allows the surrounding part of the closure skirt to deform radially inwardly as the skirt effectively acts as an inextensible but 75 flexible hoop transforming itself from a truly circular configuration to a slightly oval or elliptical configuration. This effect results in undesirable change in the shape of the closure, likely to be made more noticeable if the closure is provided with a 80 tamper-evident ring at its skirt lower rim and not subject to such radially inward and outward deformation. Furthermore the result could be that the closure rises sufficiently forthe seal provided by the conventional closure sealing gasket against the 85 upper end face of the rim of the containertofail.

Such inward deformation of the part of the closure skirt immediately surrounding the zone 6 of no thread overlap is resisted in accordance with the present invention by virtue of thefact thatthe extra 90 long closure skirt internal thread portions will in all rotational positions of the closure surround the equiangularly spaced (in this case diametrically opposed) zones 6 of non-overlap and will therefore limit the extentto which the closure skirt is ableto 95 deform inwardly atthe zones 6. Thus the thread tip of the closu re th read I i m its i n wa rd m ovem ent of the closure skirttowards the part of the neck finish cylinder 3 in the zone of non-overlap 6 and hence an inextensible closure skirt will be incapable of 100 sufficient radially outward displacement upon upward axial thrust of the closure to permit the closure seal to be broken orto allow noticeable closure distortion from the truly circular configuration.

105 Generally the thread portions 8a and 86 of the closure are overlapping and able to intersect every position of the generatrix of the closure skirt, in order to provideforsubstantially the whole of the periphery of the container rim 3 to be closely 110 surrounded by the thread tip of a closure skirtthread 8a or 86.

In the preferred form illustrated in Figures 1 and 2, the container rim thread portions 4a and 46 each extend over less than 180° and are arranged so that 115 they do not overlap atthe mould parting lines 7. On the other hand, each closure skirtthread extends over at least 180° of the closure, and preferably substantially 3/4 turns (270°) of the closure in orderto provide the desired effect at thezone of non-overlap 120 6.

If it is desirable to adopt a container external mould consisting of more than two mould parts, for examplethree mould parts,then itisequallyfeasible forthe multi-start thread on the rim of the container 125 to have more than two starts,for example there may be th ree th read sta rts i n th e case of a th ree-part mould. However, even in this case there will be a non-overlapping arrangement of the container rim thread portions atthe parting lines and there will 130 preferably be adequate peripheral extent of the

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severalthread portions (for example three) ofthe multi-start thread internally ofthe closure skirt so as to ensure that each ofthe several zones 6 of non-overlap (in the example three) has every 5 generatrix ofthe closure skirt in that position intersecting one ofthe closure skirtthread portions.

As indicated above, it is envisaged thatthe closure to be used with the container shown in Figure 1 will be equipped with a tamper-evidentfeature. Any 10 suitabletamper-evidentarrangementcanbeused.

Furthermore, it is envisaged thatthe closures to be used with the container of Figure 1 may embody the barrier label characteristic of our British Patent Application No. 8604881 or may have a barrier 15 coating of the type disclosed in our British Patent Application No. 8531717.

Furthermore, although glass and rigid plastic have been quoted above as the possible materialsforthe container, any other relatively rigid material may be 20 used. Furthermore, such a relatively rigid material, including polyethylene terephthalate, may be coated with a barrier coating such as a coating of polyvinylidene chloride.

Although the above-described embodiment ofthe 25 invention shows a glass jar, the container may be of any other form, such as a bottle, which has a threaded rim or neck.

Figure 3 shows a side elevational view, similarto that of Figure 1, but showing only a detail and also 30 showing the position of oneform of threaded closure to fit on the container. In this case the container is a tall jar.

Figure 4 shows an alternative embodiment in which the container closure is much the same as that 35 shown in Figure3butwherethecontainerisabottle having an outwardly projecting bead 11 belowthe threads ofthe container rim. This bead 11 serves to faci I itate tra nsfer of a hot mou Ided bottle from the mould station to a cooling location.

40 Figure 5 shows yet a further possibility in which the underside of the threaded neck region borders on a transfer groove 12 below which is an outwardly extending bead 13 co-operating with a radially inwardly extending bead 14 of a tamper-evident 45 feature 15 atthe foot ofthe bottle closure skirt. In this particular embodimentthe tamper-evidentfeature includes a tear-off peripheral strip 16 which has to be removed before the closure proper, 17, can be removed. However, any other suitable form of 50 tamper-evidentfeature, such as a direct bridging between the rim oftheclosure 17 and the tamper-evident ring 15, can be used.

It will of course be understood that because ofthe generally tapering cross-section of the thread 55 portions ofthe neck rim ofthe container, awayfrom the neck mould parting line 7, there will not beany noticeable interference between the container neck thread portions and the mould parts.

Although, above, the closure has been exemplified 60 as a mou Ided screw cap, it may instead be made of metal sheet and may either be pre-threaded with its multi-start thread or be rolled-on to the threaded container neckas the way of forming the threads.

Claims

I. A moulded threaded container having a rim provided with a multi-start thread, the thread consisting of at least two non-overlapping thread

70 portions arranged such that at least atthe parting line ofthe container mould parts the container rim generatrix fails to intersect any of the container rim thread portions at least in the main extent ofthe thread awayfrom the thread run-out portions.

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2. Acontaineraccordingtoclaim 1 whereininthe vicinity of said container mould part parting line the generatrix of the container rim does not i ntersect a ny ofthe extent of said thread portions, including the thread run-out portions thereof.

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3. Acontaineraccordingtoeitheroneofthe preceding claims wherein in the vicinity ofthe container rim mould part parting lines there is a circumferentially extending zone in which all ofthe container rim generatrices fail to intersect any part of

85 said container rim thread portions.
4. A container according to any one ofthe preceding claims, wherein it isformed using two diametrically opposed external mould parts forthe container, mounted for movement towards and

90 awayfrom a parting plane, and wherein the container rim multi-start thread is a two-startthread with non-overlapping thread portions.
5. The combination of a container according to any one ofthe preceding claims, with a closure

95 having a multi-start thread with the same number of thread starts as the container and with the peripheral extent ofthe thread portions ofthe closure thread considerably in excess ofthe peripheral extent ofthe thread portions ofthe container rim thread. 100
6. The combination of a threaded moulded container and a threaded closure, wherein the thread ofthe container is a multi-start external thread on a cylindrical container rim andthe thread ofthe closure is a multi-start internal thread, wherein the 105 thread portions ofthe container rim are non-overlapping, wherein the container rim mould parting lines occur where said container rim thread portions are non-overlapping, and wherein the thread portions ofthe closure skirt are mutually 110 overlapping such that at all positions around the closure skirtthe generatrix ofthe closure skirt intersects at least one of thethread portions ofthe closure skirtthread.
7. A container and closure according to claim 5 or 115 6, wherein the closure is moulded of plastic and has a tamper-evidentfeature.
8. A container and closure according to claim 5,6 or7, wherein the closure is moulded with an integrally moulded label serving as an oxygen

120 barrier.
9. A container and closure according to claim 5, 6,7 or 8, wherein the closure is moulded of a gas-permeable material and is then provided with a barrier coating of higher impermeability to gas, at

125 least in the end panel ofthe closure.
10. A container and closure according to any one of claims 5 to 9, wherein the closure is moulded of a material including at least onefiller.
II. A container according to any one ofthe 130 preceding claims, when in the form of a jar.

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12. A container according to any one of claims 1 to 9, when in the form of a bottle.
13. A container substantially as hereinbefore described with reference to and as illustrated in

5 Figures 1 and 2 ofthe accompanying drawings.
14. The combination of a container and closure substantially as hereinbefore described with reference to, and as illustrated in, Figure 2 ofthe accompanying drawing.

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15. Acontainersubstantially as hereinbefore described with reference to Figure 3 or Figure 4 ofthe accompanying drawings.
16. A container and closure combination substantially as hereinbefore described with 15 reference to, and as illustrated in, Figure 5 ofthe accompanying drawings.

Printed for Her Majesty's Stationery Office by Croydon Printing Company {UK) Ltd, 9/87, D8991685.

Published by The Patent Office, 25 Southampton Buildings, London, WC2A1 AY, from which copies may be obtained.