EP3817990A1

EP3817990A1 - Screw closure with controlled seal

Info

Publication number: EP3817990A1
Application number: EP19736350.0A
Authority: EP
Inventors: Günter Krautkrämer
Original assignee: Bericap GmbH and Co KG
Current assignee: Bericap GmbH and Co KG
Priority date: 2018-07-05
Filing date: 2019-07-02
Publication date: 2021-05-12
Anticipated expiration: 2039-07-02
Also published as: CN112469637A; DE102018116295A1; EP3817990B1; PL3817990T3; WO2020007832A1; US11939124B2; US20210206545A1; ES2974514T3; BR112020024220A2; CN112469637B; EP3817990C0

Abstract

The invention relates to a plastic closure for placing on the neck of a liquid container in a formfitting and sealing manner, comprising a head plate (1), which is provided for covering a container opening, an outer seal (7), which is circumferential along the edge of the head plate (1) and is provided for engaging with the exterior of a container neck (20) that defines the container opening, and an inner seal (5) which is circumferential within the outer seal (7) and parallel to same and which is provided for engaging with the inner face of the container neck. The outer and the inner seal (7, 5) each extends approximately perpendicularly or at a slight angle to the inner face (11) of the head plate (1). In order to provide a closure and to provide a container with a closure which generally prevent the closure from being blown off under high positive pressures, the outer seal (7) has a weakened region (6, 6', 6'') in at least one circumferential section such that the outer seal (7) becomes unsealed at a lower internal positive pressure than when the outer seal is formed without the weakened region.

Description

Screw cap with controlled seal

The present invention relates to a plastic closure for positive and tight placement on the neck of a liquid container with a head plate provided for covering a container opening and an outer seal running approximately parallel to the edge of the head plate, which is intended for engagement with the outside of a container neck defining the container opening is, as well as inside the outer seal and parallel to this circumferential inner seal, which is intended for engagement with the inside of the container neck, wherein the outer and the inner seal each protrude from the inside of the head plate in the direction of the container neck.

The circumferential seals essentially extend parallel to one another and approximately perpendicularly or slightly inclined to the plane defined by the head plate.

In particular, the invention relates to a screw cap made of plastic for liquid containers, the screw cap comprising a head plate, a cylindrical cap jacket with an internal thread that defines an axis of the closure, and an annular inner seal that is to be brought into engagement with the cylindrical inner surface of the container neck after application to the container neck and has an annular outer seal to be brought into engagement with the cylindrical outside of a container neck, the outer and inner seals each extending in a predominantly axial direction from the inside of the head plate.

Such plastic closures are used, among other things, for beverage bottles. The present invention relates in particular to closures for such containers in which an uncontrolled excess pressure can arise. This applies, for example, to containers which are filled with a fermentable liquid and in which a considerable overpressure can build up (after contamination with germs).

Such containers, when filled with the products in question, generally do not have a high internal pressure, with the exception of a slight overpressure which is specifically applied by filling with an inert gas and which essentially serves to keep the bottles, which are mostly consist of thin-walled PET material, to make it stable overall and thus stackable, typically several containers are combined into a bundle and are stacked on top of one another in this form.

In some market segments, the desire of consumers to keep the contents of the container as pure and natural as possible and the content in question, e.g. Fruit juice or smoothies, not preservable with preservatives. It goes without saying that such beverages have a comparatively short shelf life after first opening, even if they were bottled under aseptic conditions. It can therefore happen that a consumer leaves such a container for a longer period of time after shopping, especially after opening it for the first time, and possibly also in an unfavorable (warm) place, due to an initially low level of contamination in the the liquid contained in the container can begin fermentation processes. Fermentation typically produces gases, which in turn increase the pressure inside the container in an uncontrollable manner. Even if the containers and the corresponding closures are designed for a slight excess pressure (for example 2 bar) in order, as mentioned above, to facilitate stacking of the containers, a pressure resulting from fermentation can be many times higher than that alone Ensure the stackability required pressure under which the containers were originally filled with an inert gas.

As is customary in the prior art, the closure according to the invention has two mutually independent seals, one of which comes into sealing contact with the inside, the other with the outside of a corresponding container neck (deleted text shifted to page 3 :)

Since the containers, with the exception of the low overpressure already described, are essentially pressure-free to maintain stackability, the closures used for this purpose are generally relatively short axially and also have a relatively steep, mostly multi-start thread, which allows the container to be opened and closed quickly , on the other hand, the closure offers only a comparatively small hold, and also allows ventilation or venting of the container during the short opening process only to a limited extent.

This leads to the fact that when an attempt is made to open a container under relatively high internal pressure, the closure is explosively blown off the container after only a short angle of rotation and can severely injure a user, in particular if sensitive body parts, such as an eye , from the detached closure. The invention is of course not limited to this special application, but relates to closures for all containers in which an overpressure of z. B is more than 4 bar, especially if such overpressure can arise in an uncontrolled manner.

The inner seal withstands only a limited overpressure due to its geometric arrangement and design. To limit the internal pressure through the internal seal, therefore, either no or only minor additional measures are required, as will be explained below. However, the external seal can withstand a very considerable excess pressure in the known closures.

Against this background, the present invention is based on the object of providing a closure and also a container with a closure, which generally prevent the closure from breaking off under high excess pressure.

This object is achieved in that the outer seal has a weakened area in at least one circumferential section, the closure being designed such that the outer seal yields in the weakened area at a lower internal pressure than without the weakened area, especially in the weakened area, yields earlier than in the other areas.

In the case of a screw cap, the weakening area preferably extends over an angle sector measured with respect to the axis, which depending on the type of weakening can be limited to less than 1 ° circumferential angle, but in other embodiments also to an angle sector of 20 to 90 °.

Under certain circumstances, the weakened area could also extend over the entire circumference, for example in the form of a spiral groove.

More generally speaking, the task is solved in that the closure does not allow a correspondingly high overpressure to arise from the outset, i.e. leaks and gas escapes when the pressure inside the container exceeds a certain, predeterminable level, and that without an additional pressure valve to be attached.

The lower section (facing away from the head plate) of the inner seal is typically chamfered radially inwards and at the end is curved inwards in order to ensure when the closure is placed on the container neck that the inner seal slides into the opening of the container neck. The lower end of the inner seal has therefore when the outer bead on the Is inside the container neck, a clear clearance to this inside. In addition, the inner seal on its outside has a radially outwardly projecting area or bulge which, after corresponding compression by the container neck, rests against the inside of the container neck under elastic prestress.

An excess pressure which arises in a container provided with the closure generally causes the top plate of the closure to bulge. The inner seal is moved a little way up to the free opening of the neck, and at the same time the inner seal tilts radially inwards and the pressure of the gas or liquid which can act on the lower section of the inner seal from the outside additionally contributes to a radially inward Swiveling the inner seal so that it lifts off at least locally from the inside of the container neck at a certain excess pressure. The inner seal will then leak.

The internal pressure then acts on the outer seal. The bulging of the head plate also results in a reduction in the diameter of the outer seal, at least on your attachment to the head plate, which leads to an even tighter pressing of the outer seal on the container neck. Without measures to reduce the internal pressure, there is then the risk of sudden detachment when the closure is opened.

As a result of the weakening area of the outer seal specifically provided according to the invention, the outer seal also yields at a lower pressure than would be the case if the outer seal had no weakening area. As a result, the otherwise higher internal pressure is reduced and the risk of a closure being blown off from the container neck is completely or at least largely eliminated. The weakened area is therefore a means of deliberately limiting overpressure.

By appropriate geometric design of the weakening area, which can also be determined experimentally, the desired overpressure value at which the weakened area yields to the outer seal and allows the gas under pressure in the container (partially) to escape can be set well. As a rule, the weakened area will be set so that the pressure at which the outer seal opens in the weakened area is slightly above the overpressure with which the container is filled anyway for reasons of stability, i.e. with a pressure between 1 and 2.5 bar , the exact adherence to certain pressure values not being important as long as the opening pressure of the weakening area is clearly below the values that could cause the closure to come off the container neck dangerously. A reasonable upper limit for the internal pressure of containers, which are intended for carbon-free, for example, is around 3 - 4 bar for a closure with a two-start thread with a 360 ° wrap angle and a nominal diameter of 38 mm. Such a reasonable upper limit for the pressure varies with the diameter of the neck and the design of the thread and can tend to be larger with a smaller diameter and also smaller with a larger diameter.

The outer seal of the screw closure according to the invention expediently has a region which is referred to below as the sealing region and which is generally regarded as the axial region which comes into sealing contact with a container neck. Specifically, without reference to a (generally standardized) container neck, this is an area of the outer seal with a constant inner diameter that at least partially encompasses the middle third of the axial length of the outer seal. Because of a rounding on the outer edge of a container neck opening, as is provided as standard for most containers in question, in order to ensure that the outer seal slides onto the outside of the container neck when the closure is placed on the container neck, the area near the head plate of the outer seal occurs with the container neck not or hardly in contact.

The end of the outer seal, which is remote from the head plate and is in the form of a ring or ring web, is (seen in an axial section) generally slightly curved or beveled radially outwards, likewise in order to slide onto the container neck when the closure is placed on it To facilitate the neck of the container, the outer seal being expanded and stretched radially overall so that it rests against the container neck under elastic prestress and in this way resists a relatively high internal pressure. In this respect, it can be assumed that the sealing area of an outer seal comprises at least part of the central axial third of the outer seal, and the sealing area can then be defined accordingly with reference to the closure alone.

The radially outwardly curved lower end section of the outer seal is therefore not in contact with the neck of the container and cannot make any significant contribution to the sealing. The actual sealing area of the outer seal is located in the middle third, based on the axial length of the outer seal. This is the sealing area defined above, which according to the present invention is to be influenced by targeted measures or to be set to a specific opening pressure.

According to a variant of the invention, it is provided that the weakened area consists of a circumferential section of the outer seal, which has a reduced wall thickness compared to the rest of the outer seal, the outer seal in this weakened area having the same inner radius as the outer seal, but a smaller outer radius. Due to the constant internal diameter, such an outer seal lies along its entire circumference with the sealing area on the outer surface of a container neck seals well within the required pressure range for which the container and closure are designed under normal conditions. However, since the wall thickness in the weakened area is less than the outer seal in its remaining area, this section of reduced wall thickness can be more easily stretched and pressed radially outwards in the event of overpressure in the interior of the container, so that the outer seal in this area leaks when the Pressure exceeds a predetermined limit.

As a result, such a configuration provides a closure which is completely sealed under normal circumstances and which is completely sealed off by both an inner seal and an outer seal, the head plate bulging only strongly in the case of a larger (e.g.> 4 bar) internal pressure, as a result, the inner seal tilts radially inward and lifts axially and / or radially from the inner surface of the container neck, whereupon the greater pressure then acting on the outer seal is reduced over the respective weakened area.

In one embodiment of the invention, the reduced wall thickness in the axial direction extends from a free axial (lower) end to the upper third of the outer seal, based on the axial length of the outer seal outside the weakened area.

To lift the inner seal, among other things also when the maximum outer diameter of the inner seal, i.e. H. of the so-called “bead” of the outer seal, is provided at an axial distance between only 0.4 and 1.2 mm, preferably less than 1 mm, from the stop surface, so that this area is very resistant to any movements of the head plate, in particular a bulge is strongly influenced and thus lifts off from the inner surface of the container neck at least after reaching a certain excess pressure and at least in places. Gas (or liquid) under excess pressure can then escape into the area in front of the outer seal, the weakened area of the outer seal limiting the pressure which is created by allowing the gas under pressure to pass if a limit pressure is exceeded. If the head plate bulges sufficiently, the sealing bead of the inner seal, which defines its maximum diameter, can be raised in the area of the rounding of the inner edge of the bottle neck or beyond, so that the inner seal definitely gas towards or into the outer seal Area between the outer and inner seal.

According to another embodiment, it is provided that the weakened area consists of a circumferential section of the outer seal that is axially shortened in the angle sector a. Because the outer seal is shortened in a circumferential section and the shortening also covers the sealing area, there is only an axially very short section of the angular sector Sealing area on the outside of the neck of the container, which leads to the fact that the outer seal in this weakened area alone by the fact that it is also lifted a little bit axially by the bulging head plate, with a relatively low pressure inside the container yields and locally lifts off the bottle neck, so that any excess pressure is reduced in this way. At the same time, such an axially shortened sealing area is still sufficient to ensure a seal of the screw cap in the unpressurized state, ie when the pressure on both sides of the outer seal is approximately the same or limited to the regular excess pressure (<2 bar) of the container. In particular, one embodiment provides that the axial length of the outer seal in the weakening region is less than two thirds of the axial length of the outer seal outside the weakened region.

This measure, too, causes the outer seal and thus the closure to leak at a significantly lower internal pressure or reduces an increased internal pressure earlier. as a closure with an outer seal without the weakened area. Without a weakening, as is provided according to the present invention, the outer seal remains sealed until a PET bottle is burst.

The two aforementioned embodiments can also be combined with one another without any problems. as shown in the embodiment of Figure 1. In the case of a combination of a weakening section with reduced wall thickness and axial shortening of the outer seal in the same circumferential sector or section, the axial shortening can be approximately one third compared to the outer seal in the remaining area and the wall thickness should be less than half the wall thickness of the outer seal outside the weakened area amount, the reduced wall thickness extending axially into the upper third of the outer seal, based on its axial length outside the weakened area.

According to a further variant it is provided that a groove or a rib runs on the inner surface of the outer seal, which in any case extends over the axial width of the sealing region of the outer seal. A corresponding groove would provide a sealing channel that bridges the sealing area, via which gas under pressure in the interior of the container, which may have already passed through the inner seal, can be discharged to the outside without the pressure inside the container continuing elevated.

A web or a rib, which protrudes radially inwards on the surface of the outer seal and otherwise also extends over the axial width of the sealing area, acts in a similar way, since on both sides of such a rib the sealing surface of the outer seal from the Bottle neck is raised, and in this way also forms a passage for gas under pressure.

As a result, these embodiments have an outer seal that permanently has a deliberately set, small leak. This leak can already by a kapillararti passage of z. B. 0.03 mm ² cross section allow sufficient gas to pass, such as is released in a fermentation process, for example. When dimensioning the cross-section of a capillary-like passage that is specifically provided, it may also be taken into account that, in the case of a closure that is loaded with liquid from the inside (e.g., an overturned bottle or an overhead bottle), this passage may also have to allow liquid to pass through. On the other hand, such a capillary opening is not a problem under normal sales and storage conditions, because under such conditions the inner seal still effectively seals the interior of the container from the environment.

However, if possible, it should also be prevented that such a groove or protruding areas of a sealing surface, such as those caused by a rib, cause contamination and, in particular, germs causing fermentation to reach the mouth of the container neck and possibly into the container neck through the outer seal can. For this reason, a corresponding groove and analogously also a corresponding rib should have the smallest possible cross-section which meets the above conditions and which, for example, is less than 0.05 mm ² , in particular less than 0.02 mm ² , with a corresponding groove and analog a corresponding rib, for example, could have a width and a depth of 0.1 mm each, so that the total cross section does not exceed 0.01 mm ² . The flow cross-section, at least for gas, can also be significantly below the aforementioned values and, for example, only be 0.0001 mm ² , which is sufficient to reduce a slowly increasing gas pressure, but on the other hand to prevent the ingress of contaminants and germs, as long as there is no reverse pressure difference opposes a great resistance.

With such a small passage, a prevailing pressure inside the container, which also lifts the inner seal from its engagement with the inner surface of the neck of the container, is reduced only very slowly and essentially continuously.

As far as no excess pressure or excessive excess pressure arises in the interior of the container, the internal seal in any case prevents the penetration of pathogens and the like into the container and the risk that possibly only the mouth of the container neck is contaminated is in the above-described embodiments with groove or rib on the inner surface of the outer seal is very small in view of the small cross section of the groove or the rib. To make it easier to lift the inner seal from the inner surface of the container neck, the fact that the inner seal has an axial length of at least 2 mm with an end section that tapers conically from its maximum diameter to one end axially in front of one end also helps. The pressurized gas in a container has no axial counterpart in the conical area outside the inner cross section of the inner seal and can thus contribute to the inner seal being pressed radially inward and thereby becoming leaky

Overall, it has also proven expedient for the inner seal to give way in the event of excessive internal pressure if the maximum outer diameter of the inner seal is at least 1.5 mm larger than its maximum inner diameter.

In general, the maximum outer diameter of the inner seal is also smaller than the minimum inner diameter of the outer seal, because a container neck opening has to be included between them, the corresponding run-up bevels and roundings on the seals and / or on the container neck opening making it possible for the maximum outer diameter of the inner seal and the minimum diameter of the outer seal differs only slightly, and in particular by significantly less than it corresponds to the wall thickness of the neck of the container.

The head plate has an annular section between the outer and inner seal, which defines an axial stop surface for the end face of a container neck opening. The wall thickness in the area of this annular stop surface can be the same as in the central area of the head plate, but it can in particular also be larger or smaller, the latter being preferred in order to make the head plate easier to move so that it is more inside the container when overpressure occurs bulges.

In this respect, the invention also relates to a container with a plastic closure, the container having a container neck which is designed for the form-fitting and tight engagement with a plastic closure according to one of claims 1 to 14. In particular, the invention also relates to a container which has a container neck with an external thread and a screw cap, the maximum outer radius of the inner seal being 0.2 to 0.4 mm larger than the nominal inner diameter of the bottle neck. Conversely, the inner diameter of the outer seal, which is constant in the sealing area, is also 0.2 to 0.4 mm smaller than the nominal outer diameter of the neck of the container. This ensures that both seals bear under prestress on the inside or outside of the container neck, while its end face axially abuts the annular stop face of the head plate, which lies between the outer seal and the inner seal. Further advantages, features and possible uses of the present invention will become clear from the following description of preferred embodiments and the associated figures. Show it:

1A shows a section containing the axis of a closure through a screw cap placed on a bottle neck according to a first embodiment of the invention, the illustration being limited to the area of the seals and showing a normal section of the outer seal.

Figure 1 B shows a section perpendicular to the axis of the closure in Figure 1A along the section line B-B

Figure 2 shows a section corresponding to Figure 1A of a closure on a container under increased internal pressure.

3A shows a section through the section of the same closure according to FIG. 1A diametrically opposite the section according to FIG. 1A with an outer seal weakened in one segment

Figure 3B shows a section along the line B3-B3 in Figure 3A

4 shows a view according to FIG. 3A with an additionally drawn contour of the outer seal outside the weakened area.

FIG. 5A shows a plan view of a section of the inner surface of an outer seal according to a further embodiment, which has a cutout in the sealing area.

FIG. 5B shows a horizontal section through a closure according to FIG. 5A, the section plane running through the cutout and the section showing only a section of the closure on a bottle neck

6A shows a plan view of a section of the inner surface of an outer seal according to a further embodiment, which has a projection in the sealing area.

6B shows a horizontal section through a closure according to FIG. 6A, the section plane running through the projection and the section showing only a section of the closure on a bottle neck

7A shows a section analogous to FIG. 1A of a further embodiment

FIG. 7B shows a horizontal section through a closure according to FIG. 6A, the section plane running through the weakened area of the outer seal and the section showing only a section of the closure on a bottle neck, and

FIG. 8 For a better overview, a cross section through the complete closure according to FIGS. 1 and 3. Figure 1 shows an axial section through the edge of a container neck with attached closure 100. The container neck is described below as a bottle neck and shows the contour of a bottle neck edge of a PET bottle with 30 or 43 mm thread.

The inner seal 5 is shown here overlapping with the inner surface of the bottle neck 20, but this is only intended to indicate that the outer surface of the inner seal, in particular the bead 5 ′ provided on the outer surface, rests with elastic prestress on the inner surface of the bottle neck 20, as is also the case is shown in Figure 2, wherein Figure 2 also shows a domed by an increased internal pressure head plate 1. The increased pressure also causes the conical outer surface between the maximum diameter of the bead 5 'and the lower free end of the inner seal 5 to be acted upon by the increased inner pressure, so that from a certain inner pressure the inner seal 5 or its bulge projecting outward from the Lifts the inner surface of the bottle neck 20 and thus allows the pressure to escape into the area between the outer seal 7 and the inner seal 5.

The state shown in FIG. 2 corresponds to a situation in which the inner seal 5 has been raised and tilted to such an extent that it is lifted off the inner surface 22 of the bottle neck and is leaking. The rounding provided on the inner upper edge of the bottle neck in accordance with customary standards in turn contributes to the fact that the inner seal, at least locally, loses the sealing contact with the bottle neck at least locally.

A part of the closure 100 can be seen in FIG. 1A, which has a head plate 1, a cap jacket 2 with a screw thread 3 and an inner seal 5 and an outer seal 7. When the closure 100 is screwed onto a bottle neck 20, the mouth of the bottle neck 20 slides between the outer seal 7 and the inner seal 5, generally until the end face 24 of the bottle neck mouth abuts a stop face 4 of the annular section 14 on the underside the head plate 1, which is located between the two seals 5 and 7.

The conically inwardly tapering lower section of the inner seal 5 and the conically or rounded lower section of the outer seal 7, as well as the roundings at the upper edge of the bottle neck mouth, contribute to the bottle neck 20 being in between when the closure 100 is put on pushes the inner seal 5 and the outer seal 7 and does not compress a seal which strikes the end face 24 of the bottle neck. Figure 2 shows (again only in a section) a bulging head plate 1 under increased internal pressure, so that the internal pressure triggers a leak in the inner seal 5, the clear distance between the bead 5 'of the inner seal 5 and the inside 22 of the bottle neck 20 to Clarification of the effects occurring is somewhat exaggerated. Due to the bulging of the head plate 1, which is also favored by a smaller wall thickness d of the head plate 1 in the area of the annular section 14 of the head plate 1 (see FIG. 4), the inner seal 5 tends to be tilted inwards, as initially done by the radial inward pushing of the bead 5 'occurs when engaging with the inner sealing surface of the bottle neck 20. In the area radially inside the inner seal 5, the top plate 1 has a somewhat larger wall thickness D, the different wall thicknesses d, D not being a mandatory feature, but which can favor or simplify the desired overpressure limitation of the closure.

As an alternative to a reduced wall thickness of the annular section 14 or additionally, a groove can be provided on the inside of the head plate 1 at the transition from the stop surface 4 and the inner seal 5, which groove makes the inner part of the head plate 1 with the inner seal 5 even more mobile than the radially outer one Section 14 does what the bulging of the head plate 1 and the tilting and axial lifting of the inner seal 5 up to leakage again facilitates. With a sufficiently high internal pressure, which also acts on the outside of the inner seal 5, provided that it has no opposite pressurized surface in the axial direction, the bead 5 'lifts off at least in some places from the inner surface 22 of the bottle neck 20, so that the Pressure can escape until the bulge of the head plate 1 has decreased accordingly and the elastic restoring forces of the inner seal bring the bead 5 'of the inner seal 5 back into sealing engagement with the bottle neck.

FIG. 3A shows the same closure as FIG. 1A, but the sectional plane runs through a weakened area 6 of the outer seal 7.

The weakened area 6 in this case consists of an optionally axially shortened and reduced in wall thickness section 6 of the outer seal 7, which has the same inner diameter as the outer seal 7 in the rest of the area, but has a significantly smaller outer diameter. Figure 3B shows a section through the line B3-B3 in Figure 3A. The inner seal 5 lies against the inner surface 21 of the bottle neck 20 (the overlap of the inner seal 5 with the bottle neck 20 in FIG. 3A is only intended to represent the tension-free state before the inner seal 5 or its bead 5 ′ is pressed inwards by the bottle neck) ,

The upper third of the outer seal 7 adjoining the head plate is located in the region of a radius of curvature at the upper edge of the neck opening and thus does not come into contact with the The bottle neck and the lower third are already radially widened in order to facilitate the sliding of the mouth of the bottle neck 20 into the space between the two seals 5 and 7 when the closure is placed on a bottle neck. If the seal 7 is now shortened to half or the entire axial length of the outer seal 7 over a certain angle sector a, which may be 30 °, for example, only a relatively axially relatively short section of the outer seal 7 with the outer side 21 of the bottle neck is left in this area 20 in contact, wherein a relatively small excess pressure within the outer seal 7 is sufficient to lift this relatively short, still sealing section from the outside 21 of the bottle neck 20 and thus to relieve pressure.

The outer seal 7, of which two end sections can still be seen in the angular section shown in FIG. 3B, is not only shortened axially in the weakening segment within the angular sector a, but is also replaced by a weakened area 6 with reduced wall thickness, which, however, has the same inner diameter as the inner seal 7 otherwise. Under normal conditions, i.e. if no or only a slight overpressure of e.g. B. 2 bar prevails in the area between the inner seal 5 and outer seal 7, the weakening area 6 of the outer seal is thus sealing against the outside 22 of the bottle neck 20 and protects against the ingress of germs before first use, d. H. on the way from the bottler to the consumer.

The dimensional relationships between the weakened area 6 of the outer seal 7 are also illustrated again in FIG. 4, where, in addition to the weakened area 6 shown in section, the contour of the outer seal 7, as is present in the areas of the outer seal 7 outside the weakened area 6, was also drawn. It can also be seen in FIG. 4 that the wall thickness d of the head plate in the area between the inner seal 5 and the outer seal 7 is somewhat less than the wall thickness D radially inside the inner seal 5.

FIG. 8 shows the complete closure in the sectional plane of FIGS. 1A and 3A. 1A corresponds to the area I with a dashed frame in FIG. 8 and FIG. 3A corresponds to the area III with a dashed frame in FIG. 8.

In the weakened area 6 on the right-hand side of FIG. 8, the outer seal 7 is axially shortened and its wall thickness is reduced, as a result of which the outer seal 7 in the weakened area 6 is more easily stretchable and yields at a lower internal pressure than is the case with a uniform design of the outer seal 7 with full wall thickness and axial length as would be the case in area I and the rest of the area. FIG. 5A shows a small section of the head plate 1 with the seal 7 extending downward from the head plate 1, FIG. 5A being a plan view of the inner surface of the outer seal 7, which normally comes into sealing contact with the outer surface 22 of the bottle neck.

In this case, the inner surface of the outer seal has a small groove-like recess 6 ', which bridges in the axial direction the area in which the seal otherwise lies tightly against the outer side 22 of the bottle neck 20. This is shown again schematically in a section running through the recess 6 'in FIG. 5B. For practical purposes, it is sufficient if the cross section of the groove-like recess 6 ', as can be seen in FIG. 5B, is less than 0.5 mm ² , in particular less than 0.2 mm ² . The recess 6 'which is approximately semicircular in the section according to FIG. 5B could, for example, have a radius of 0.1 to 0.2 mm.

FIGS. 6A and 6B represent a further embodiment, in which instead of a recess 6 ', a radially inwardly projecting web or a rib or a projection 6 "is provided. Even if the wall thickness of the outer seal 7 in the circumferential direction of the outer seal and on both sides of the projection or the rib 6 "is constant, short sections of the inner seal 7 are nevertheless lifted off the outer surface 22 of the bottle neck 20 on both sides of the rib 6", which effectively leads to the fact that on both sides of the rib 6 ″, in turn, two small recesses 6 ′ which are wedge-shaped in cross section are formed. Here too, the rib 6 ″ is dimensioned such that the total cross section of the recesses 6 ′ thus formed is not more than 0.5 mm ² , preferably less than 0.2 mm ² . It goes without saying that here, too, the rib 6 ″ extends in a straight line or curved in the axial direction over the sealing area of the outer seal 7, so that the recess 6 ′ connects the space between the outer and inner seal to the outside of the bottle neck 20.

FIG. 7 finally shows yet another embodiment in which the outer seal 7 has been axially shortened in an angular range a, so that in the angular sector a of the weakened area 16 only a very small contact axially between the outer seal 7 or the weakened area 16 and the bottle neck 20 or whose outer surface 22. This is dimensioned such that when the head plate is arched, the outer seal, despite its proximity to an imaginary pivot point of the bulged part of the head plate 1, still shifts axially upwards sufficiently to open a gas passage.

The invention is essentially based on two effects, namely on the one hand, to use the arching of the head plate which arises under internal pressure, in order first to open the inner seal to such an extent that undesirably high internal pressure of e.g. B more than 3 bar is passed on to the outer seal. Secondly, this outer seal is the same at least in an angular sector weakened that when exposed to the z. B. 3 bar pressure also yields and the pressure can be reduced by gas leakage from the container.

These effects are achieved, inter alia, by using the material polyethylene, in particular HDPE for the closure, in conjunction with a wall thickness of the head plate of less than 2 mm, preferably less than 1.0 mm, and an inner seal, the bead of which is relatively close to the head plate lies and seals there and is axially displaced far enough with increased internal pressure when the relevant area of the head plate moves. The invention also relates in particular to a combination of a container neck or a container with a plastic closure, the maximum outer diameter of the outer seal being between 0. 2 and 0.4 mm is larger than the corresponding inner diameter of the container neck opening, while the inner diameter of the outer seal is also approximately 0.2 to 0.4 mm smaller than the corresponding outer diameter of the container neck in the respective angular position. The closure according to the invention is particularly well suited for containers with cylindrical cylinder necks which have an inner diameter of 40 or 30 mm, but can also be used for smaller closure diameters of, for example, 28 mm. The embodiments described above are therefore adapted in terms of their dimensions to corresponding standardized container necks or bottle necks.

reference numeral

1 headstock

2 cap jacket

3 screw threads of the closure

4 stop surface (inner surface of the head plate between the seals 5, 7)

5 inner seal

5 'radially projecting area, bead

6 weakening area

7 outer seal

a angular sector

11 inner surface of the head plate

14 Annular section of the head plate 1 with the stop surface 4

16 weakening range

20 bottlenecks

21 Outside surface / outside of the bottle neck

22 Inner surface of the bottle neck

100 closure

Claims

Patent claims

1. Plastic closure for positive and tight placement on the neck of a liquid container with a head plate (1) provided for covering a container opening and an outer seal (7) running approximately parallel to the edge of the head plate (1), which is used for engagement with the outside a container neck (20) defining the container opening is provided, as well as an inner seal (5) which runs inside the outer seal (7) and runs parallel to it and which is provided for engagement with the inside of the container neck, the outer and inner seals (7 , 5) protrude from an inner side (1 1) of the head plate (1) in the direction of the container neck to be covered by the head plate, characterized in that the outer seal (7) has a weakened area (6, 6 ', 6 “, in at least one peripheral section), 16), the closure being designed such that the outer seal in the weakened area (6, 6 ‘, 6 ″, 16) yields at a lower internal overpressure than without the weakening area, in particular at a lower internal overpressure than in the other areas of the outer seal.

2. Plastic closure according to claim 1, characterized in that it is designed as a screw closure, the screw closure (100) having a head plate (1) and a cylindrical cap jacket (2) with an internal thread (3) which has an axis (50) of the Define the closure, the outer and inner seals being designed as webs which run around in an annular manner at a distance from the cap jacket and parallel to it, and the weakening section is preferably limited to an angular sector (a) measured with respect to the axis.

3. Screw cap according to claim 1, characterized in that it has a sealing area which is an axial area of the outer seal with a constant inner diameter, which at least partially comprises the middle third of the axial length of the outer seal and corresponds at most to the axial length of the outer seal.

4. Screw cap according to claim 1 or 2, characterized in that the weakened area (6, 6 ', 6 ", 16) is formed by a groove (6') or rib (6") running on the inner surface of the outer seal runs on the inside of the outer seal over the axial extent of the sealing area of the outer seal.

5. Screw cap according to claim 2 or 3, characterized in that the groove (6 ') or the rib (6 ") extends essentially axially and has a cross section of less than 0.05 mm ² , in particular less than 0.02 mm ² , and for example has a width and depth of 0.1 mm each.

6. Screw cap according to claim 1 or 2, characterized in that the weakened area (6, 6 ', 6 ", 16) consists of an axially shortened circumferential section of the outer seal in the angular sector (a).

7. Screw cap according to claim 4, characterized in that the axial length of the shortened peripheral section is less than 2/3 of the axial length of the outer seal outside the weakened area (6, 6 ', 6 ", 16).

8. Screw cap according to one of the preceding claims, characterized in that the weakened area (6) consists of a peripheral portion of the outer seal (7) with a reduced wall thickness compared to the rest of the outer seal (7), where the outer seal (7) in the weakened area (6 ) the same inner radius as the outer seal (7) for the rest, but has a smaller outer radius.

9. Screw cap according to claim 5, characterized in that the reduced wall thickness of the outer seal in the weakened area (6) extends axially over at least part of the central axial third of the length of the outer seal and is less than half the wall thickness outside the weakening sector, wherein the extent of the weakening region (6) in the circumferential direction is preferably limited to preferably a circumferential angle between 20 ° and 90 °, in particular between 40 ° and 70 °.

10. That the weakened area with reduced wall thickness extends axially from a free axial end to at least the upper axial third, based on the axial extent of the outer seal outside the weakened area

1 1. Screw cap according to one of the preceding claims, characterized in that an annular disk-shaped section (14) of the head plate (1) between the outer and inner seal defines an axial stop surface (4) for the end face (24) of a container neck and the maximum outer diameter the inner seal (5) is provided at an axial distance between 0.4 and 1.0 mm from the stop surface.

12. Screw cap according to one of the preceding claims, characterized in that a circumferential groove is provided in the inner surface (1 1) of the head plate at the transition from the annular disc-shaped section (4) of the head plate (1) to the inner seal (5).

13. Screw cap according to one of the preceding claims, characterized in that the inner seal (5) has an axial length of at least 2 mm with an end portion which tapers conically from its maximum diameter to its axially free end.

14. Screw cap according to one of the preceding claims, characterized in that the maximum outer diameter of the inner seal is at least 1.5 mm larger than its maximum inner diameter.

15. Screw cap according to one of the preceding claims, characterized in that it consists of polyethylene and that the wall thickness of the head plate within the area covered by the outer seal is a maximum of 1.2 mm.

16. Container for liquids with a container neck, on which a plastic closure is placed firmly and sealed, characterized in that it has a plastic closure according to one of the preceding claims 1-15.

17. A container according to claim 16, characterized in that the container neck has an external thread and the plastic closure is a screw closure

18. A container according to claim 16 or 17, characterized in that the maximum outer radius of the inner seal is 0.3 to 0.7 mm larger than the nominal inner radius of the container neck at the respective position.

19. Container with screw cap according to one of claims 16 to 18, characterized in that a constant inner radius of the outer seal, insofar as this comes into sealing contact with the outside (22) of the container neck (20), is 0.3 to 0.7 mm smaller than the nominal, constant outer radius of the container neck (20) in the area of the sealing contact with the outer seal.